Semiconductor Device

ABSTRACT

Even when a thermal stress is applied to an electrode pad, the electrode pad is prevented from being moved. A substrate of a semiconductor chip has a rectangular planar shape. The semiconductor chip has a plurality of electrode pads. The center of a first electrode pad is positioned closer to the end of a first side in the direction along the first side of the substrate as compared to the center of a first opening. Thus, in a part of the first electrode pad covered with an insulating film, a width of the part closer to the end of the first side in the direction along the first side is larger than another width of the part opposite to the above-mentioned width.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2013-182362 filed onSep. 3, 2013 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to semiconductor devices, and moreparticularly, to a technique that can be applied to a semiconductordevice with electrode pads.

Semiconductor chips have electrode pads serving as a terminal forexternal connection. The electrode pad is exposed outward from anopening provided in a protective insulating film as disclosed in, forexample, Patent Document 1. Patent Document 1 also describes that thecenter of the opening provided in the protective insulating film isdisplaced from the center of the electrode pad in a directionperpendicular to the edge of the semiconductor chip.

RELATED ART DOCUMENTS Patent Documents

[Patent Document 1] Japanese Unexamined Patent Publication No. Hei06(1994)-163629

SUMMARY

In recent years, power consumption of semiconductor chips has beenincreasing. For this reason, the inventors have studied the effect ofincreasing the thickness of electrode pads so as to suppress a wiringresistance of the inside of a wiring layer.

On the other hand, the semiconductor chip is mounted over a wiringsubstrate, such as a lead frame or an interposer, and then sealed with aseal resin. A thermal expansion coefficient of the seal resin differsfrom that of an insulator or metal used in the wiring layer. As aresult, thermal stress is generated at an interface between the sealresin and the semiconductor chip. However, when the thickness of theelectrode pad is increased as mentioned above, the thermal stress mightbe applied to the electrode pad, possibly moving the pad.

Other problems and new features of the present invention will beclarified in the detailed description below in connection with theaccompanying drawings.

According to one embodiment of the invention, a multilayerinterconnection layer is formed over a rectangular substrate. Aplurality of electrode pads is formed in an uppermost wiring layer ofthe multilayer interconnection layer. The electrode pads are arrangedalong a first side of the substrate. When the electrode pad closest toone end of the first side is defined as a first electrode pad, and theopening positioned over the first electrode pad is defined as a firstopening, a center of the first electrode pad is positioned closer to theone end in a direction along the first side as compared to a center ofthe first opening.

The above-mentioned embodiment of the invention can prevent theelectrode pad from moving even when the thermal stress is applied to theelectrode pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure of asemiconductor device according to one embodiment of the invention;

FIG. 2 is a plan view of a semiconductor chip;

FIG. 3 is a diagram for explaining the position of a first opening withrespect to a first electrode pad, and the position of a second openingwith respect to a second electrode pad;

FIG. 4A is a diagram showing the position of the first opening withrespect to the first electrode pad;

FIG. 4B is a diagram showing the position of the second opening withrespect to the second electrode pad;

FIGS. 5A and 5B are diagrams showing modified examples of FIGS. 4A and4B;

FIG. 6 is a cross-sectional view for explaining the structure of thesemiconductor chip;

FIG. 7 is a plan view showing the structure of a semiconductor chip usedin a semiconductor device according to a first modified example;

FIG. 8 is an enlarged diagram showing a main part of FIG. 7;

FIG. 9 is a cross-sectional view showing the structure of asemiconductor device according to a second modified example; and

FIG. 10 is a cross-sectional view showing the structure of asemiconductor device according to a third modified example.

DETAILED DESCRIPTION

In the following, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. Whereverpossible, the same reference numerals will be used through the drawingsto refer to the same or like parts, and thus a description thereof willbe omitted below.

Embodiment

FIG. 1 shows a cross-sectional view of the structure of a semiconductordevice SD according to one embodiment of the invention. Thesemiconductor device SD of this embodiment includes a semiconductor chipSC sealed with a seal resin MDR. Specifically, the semiconductor chip SCis held over a substrate mounting portion DP with an electrode formationsurface of the chip faced upward. The substrate mounting portion DP is,for example, a die pad of a lead frame. The semiconductor chip SC iscoupled to lead terminals LD via bonding wires WIR. The bonding wireWIR, and a coupling portion of the lead terminal LD with the bondingwire WIR are sealed with the seal resin MDR. One end of the leadterminal LD extends to the outside of the seal resin MDR.

In an example shown in the figure, the substrate mounting portion DP issmaller than the semiconductor chip SC. Alternatively, the substratemounting portion DP may be larger than the semiconductor chip SC.

FIG. 2 shows a plan view of the semiconductor chip SC. A substrate SUBof the semiconductor chip SC has a rectangular planar shape. Thesemiconductor chip SC includes a plurality of electrode pads PD. Eachelectrode pad PD has, for example, an oblong planar shape. The electrodepad PD is coupled to one end of the bonding wire WIR shown in FIG. 1.

The electrode pads PD are arranged along at least a first side SID1 ofthe substrate SUB. In the example shown in the figure, the electrodepads PD are arranged not only along the first side SID1 of the substrateSUB, but also along a side (second side SID1) opposed to the first sideSID1, and the remaining two sides (third side SIDS and fourth side SID4). The short sides of the electrode pad PD are disposed in parallelwith one of the four sides of the substrate SUB located closest to theelectrode pad PD.

In the example shown in the figure, the electrode pads PD are arrangedin line. Although the electrode pads PD are arranged at equal intervals,at least some electrode pads PD may be spaced apart from each other by adistance different from that between other electrode pads PD. Thesemiconductor chip SC is provided with a guard ring GDL. The electrodepads PD are positioned in a region enclosed by the guard ring GDL.

An insulating film PSV is formed as the uppermost layer of thesemiconductor chip SC. The insulating film PSV is, for example, a filmthat is called a passivation film, and has, for example, a laminate of asilicon oxide film and a silicon nitride film which are stacked in thatorder. The insulating film PSV serves to protect a multilayerinterconnection layer MINC of the semiconductor chip SC (to be describedlater using FIG. 5). The insulating film PSV is provided with openingsOP (to be described later using FIG. 3) positioned over the respectiveelectrode pads PD. The relative position between the electrode pad PDclosest to the corner of the substrate SUB among the electrode pads PD(hereinafter referred to as a “first electrode pad PD1”) and the openingOP positioned over the above-mentioned electrode pad (hereinafterreferred to as a “first opening OP1”) differs from the relative positionbetween the electrode pad PD closest to the center of each side of thesubstrate among the electrode pads PD (hereinafter referred to as a“second electrode pad PD2”) and the opening OP positioned over theabove-mentioned electrode pad (hereinafter referred to as a “secondopening OP2”). The difference in relative position will be describedbelow with reference to FIGS. 3 and 4.

FIG. 3 shows a diagram for explaining the position of the first openingOP1 with respect to the first electrode pad PD1, and the position of thesecond opening OP2 with respect to the second electrode pad. FIG. 4Ashows a diagram for explaining the position of the first opening OP1with respect to the first electrode pad PD1. FIG. 4B shows a diagram forexplaining the position of the second opening OP2 with respect to thesecond electrode pad PD2.

As shown in FIG. 3, the center of the first electrode pad PD1 ispositioned closer to the end of the first side SID1 as compared to thecenter of the first opening OP1 in the direction along the first sideSID1 (in the direction Y of the figure). Thus, as shown in FIG. 4A, asto a part of the first electrode pad PD1 covered with the insulatingfilm PSV in the direction along the first side SID1, a width of the partcloser to the end of the first side SID1 (on the upper side of thefigure) is larger than another width of the part opposite to theabove-mentioned width (on the lower side of the figure). In detail, asmentioned above, the short side of the first electrode pad PD1 isparallel with the first side SID1. A distance α_(l) from one of two longsides of the first electrode pad PD1 closer to the end of the first sideSID1 (or the long side on the upper side of the figure) to the edge ofthe first opening OP1 is larger than a distance α₂ from the remaininglong side of the first electrode pad PD1 (or the short side on the lowerside of the figure) to another edge of the first opening OP1. Thedistance α_(l) is, for example, in a range of not less than 5 μm normore than 20 μm, and the distance α₂ is, for example, in a range of notless than 1 μm nor more than 5 μm. A distance α₃ from one of the shortsides of the first electrode pad PD1 closer to the first side SID1 toanother edge of the first opening OP1 is larger than a distance α₄ fromthe remaining short side of the first electrode pad PD1 to another edgeof the first opening OP1. The distance α₃ is, for example, in a range ofnot less than 5 μm nor more than 20 μm, and the distance α₄ is, forexample, in a range of not less than 1 μm nor more than 5 μm.

On the other hand, as shown in FIG. 3, the center of the secondelectrode pad PD2 is substantially superimposed over the center of thesecond opening OP2 in the direction along the first side SID1 (in thedirection Y of the figure). In detail, distances β₁ and β₂ from therespective two long sides of the second electrode pad PD2 to the edge ofthe first opening OP1 are equal to each other. The distance β₁ is, forexample, in a range of not less than 1 μm nor more than 5 μm. Due to amanufacturing error, the center of the second electrode pad PD2 issometimes located closer to the end of the first side SID1 as comparedto the center of the second opening OP2. Even in this case, however, adistance from the center of the second electrode pad PD2 to the centerof the second opening OP2 is also smaller than that from the center ofthe first electrode pad PD1 to the center of the first opening OP1. Adistance β₃ from one of the short sides of the second electrode pad PD2closer to the second side SID2 to the edge of the second opening OP2 islarger than a distance β₄ from the remaining short side of the secondelectrode pad PD2 to another edge of the second opening OP2. Thedistances β₃ and β₄ are substantially equal to the distances α₃ and α₄,respectively.

In the example shown in the figure, the width of the first electrode padPD1 is set larger than that of the second electrode pad PD2 in thedirection along the first side SID1, so that the above-mentionedrelative position can be achieved with the size of the first opening OP1equal to that of the second opening OP2. In this way, the first openingOP1 does not need to be decreased in size, and thus can ensure an areafor coupling between the first electrode pad PD1 and the bonding wireWIR.

As shown in FIG. 5, a width of the first opening OP1 in the directionalong the first side SID1 is set smaller with respect to the firstopening OP1, so that the above-mentioned relative position may beachieved with the size of the first electrode pad PD1 being the same asthat of the second electrode pad PD2.

In an example shown in FIG. 3, the relative position between theelectrode pad PD other than the first electrode pad PD1 and the openingsOP thereover is the same as that between the second electrode pads PD2and the second opening OP2. Alternatively, the relative position betweenanother electrode pad PD and the opening OP positioned thereover, forexample, the relative position between the electrode pad PD adjacent tothe first electrode PD1 and the opening OP thereover may be the same asthat between the first electrode pad PD1 and the first opening OP1.

FIG. 6 shows a cross-sectional view for explaining the structure of asemiconductor chip SC. As mentioned above, the semiconductor chip SC hasthe substrate SUB. The substrate SUB is a semiconductor substrate, forexample, a silicon substrate and the like. An element isolation film EIis formed in the substrate SUB. The element isolation film EI is formed,for example, by a STI method, but may be formed by a LOCOS method. Atransistor TR is further formed over the substrate SUB. The elementisolation film EI serves to isolate the transistor TR from otherregions.

The multilayer interconnection layer MINC is formed over the substrateSUB, element isolation film EI, and transistor TR. At least one ofwiring layers included in the multilayer interconnection layer MINC (forexample, a layer with a wiring INC1 shown in the figure) is a copperwiring layer, which is formed by a Damascene method. The thickness ofthe wiring INC1 is, for example, not less than 0.1 μm nor more than 0.8μm.

A plurality of electrode pads PD are formed over the uppermost wiringlayer of the multilayer interconnection layer MINC. An insulating filmserving as an underlayer for the electrode pad PD is, for example, asilicon oxide film. The electrode pad PD is formed, for example, usingAl (or an Al alloy). A wiring INC2 is formed in the same layer as theelectrode pad PD so as to be coupled to the electrode pad PD. In orderto decrease the wiring resistance of the wiring INC2, the electrode padPD and the wiring INC2 are formed more larger in thickness than thewiring INC1. The thickness of each of the electrode pad PD and wiringINC2 is, for example, 1.2 μm or more.

An insulating film PSV is formed over the electrode pad PD and wiringINC2. The insulating film PSV is formed of a laminate of a firstinsulating film PSV1 and a second insulating film PSV2. The firstinsulating film PSV1 is, for example, a silicon oxide film, and thesecond insulating film PSV2 is, for example, a silicon nitride film. Thethickness of the insulating film PSV is larger than that of theelectrode pad PD. In the example shown in the figure, the thickness ofthe first insulating film PSV1 is larger than that of the electrode padPD.

Next, a manufacturing method of the semiconductor device SD in thisembodiment will be described. First, the element isolation film EI isformed in the substrate SUB. In this way, a region where the transistorTR is formed (element formation region) is separated from other regions.Then, a gate insulating film and a gate electrode are formed in thesubstrate SUB positioned in the element formation region. The gateinsulating film may be a silicon oxide film, or a high-dielectricconstant film having a higher dielectric constant than that of thesilicon oxide film (for example, a hafnium silicate film). When the gateinsulating film is a silicon oxide film, the gate electrode is formed ofa polysilicon film. When the gate insulating film is the high-dielectricconstant film, the gate electrode is formed of a laminate of a metalfilm (for example, made of TiN) and a polysilicon film. When the gateelectrode is formed of polysilicon, a polysilicon resistance may beformed over the element isolation film EI in a step of forming the gateelectrode.

Then, extension regions for source and drain are formed in the substrateSUB positioned in the element formation region, followed by formingsidewalls on the side walls of the gate electrode. Thereafter, impurityregions serving as the source and drain are formed in the substrate SUBpositioned in the element formation region. In this way, the transistorTR is formed over the substrate SUB.

Next, the multilayer interconnection layer MINC is formed over thesubstrate SUB, transistor TR, and element isolation film EI. In thisstep, the electrode pad PD is formed in the uppermost wiring layer. Theelectrode pad PD is formed, for example, by depositing an Al film,forming a resist pattern on the Al film, and then etching the Al filmusing the resist pattern as a mask.

Then, the first insulating film PSV1 and the second insulating film PSV2are deposited over the multilayer interconnection layer MINC in thatorder. The first and second insulating films PSV1 and PSV2 are formedusing, for example, a plasma CVD method. Thus, the insulating film PSVis formed.

Then, a resist pattern is formed on the second insulating film PSV2, andthe insulating film PSV is etched using the resist pattern as a mask.Thus, the openings OP are formed. Then, the resist pattern is removed.

Thereafter, the substrate SUB is diced to be singulated intosemiconductor chips SC.

The thus-obtained semiconductor chip SC is mounted over the substratemounting portion DP, and the electrode pads PD of the semiconductor chipSC and the lead terminals LD are coupled together using the bondingwires WIR. Then, the seal resin MDR is formed by use of a die.

Next, the effects of the preferred embodiment of the invention will bedescribed. This embodiment increases the thickness of the electrode pad,thereby decreasing the resistance of the wire located in the same layeras the electrode pad PD. In this case, the thermal stress generatedbetween the seal resin MDR and the semiconductor chip SC is more likelyto be applied to the electrode pad PD. In particular, the firstelectrode pad PD1 positioned near the corner of the substrate SUB has alarge distance from the center of the substrate SUB as compared to otherelectrode pads PD, and thus can be subjected to the larger thermalstress than other electrode pads PD. In such a case, the first electrodepad PD1 can be peeled away from the insulating layer as the underlayerto be moved.

For this reason, in this embodiment, the center of the first electrodepad PD1 is positioned closer to the end of the first side SID1 ascompared to the center of the first opening OP1. Thus, in a part of thefirst electrode pad PD1 covered with the insulating film PSV, a width ofthe part closer to the end of the first side SID1 in the direction alongthe first side SID1 is larger than another width of the part opposite tothe above-mentioned width. A region of the first electrode pad PD1 towhich the thermal stress is applied is pressed by the insulating filmPSV, which prevents the first electrode pad PD1 from being peeled awayfrom the underlayer. As a result, the first electrode pad PD1 is lesslikely to be moved.

In this embodiment, the thickness of the insulating film PSV is largerthan the height of the electrode pad PD. Thus, a stepped portion betweenthe electrode pad PD and the underlayer is filled with the insulatingfilm PSV, which can decrease a stepped portion generated at the surfaceof the insulating film PSV due to the stepped portion between theelectrode pad PD and the underlayer. With this arrangement, the thermalstress generated between the seal resin MDR and the semiconductor chipSC is less likely to be applied to the side surface of the electrode padPD.

In this embodiment, the insulating film PSV is a laminate of the firstinsulating film PSV1 and the second insulating film PSV2. The firstinsulating film PSV1 is formed of a silicon oxide film, the secondinsulating film PSV2 is formed of a silicon nitride film, and thethickness of the first insulating film PSV1 is larger than that of theelectrode pad PD. In this case, even when the thickness of theinsulating film PSV becomes larger, this embodiment can suppress theincrease in thermal stress that might be generated between theinsulating film PSV and the multilayer interconnection layer MINC.

In all electrode pads PD, a distance from one of the short sides of theelectrode pad PD close to the edge of the substrate SUB to the openingOP is larger than that from the remaining short side of the electrodepad PD (short side on the center side) to the opening OP. In otherwords, in a part of the electrode pad PD covered with the insulatingfilm PSV, a width of the part closer to the edge of the substrate SUB inthe direction getting close to the center of the substrate SUB from theedge of the substrate SUB is larger than another width of the partopposite to the above-mentioned width. With this arrangement, all theelectrode pads PD are less likely to be moved even under the thermalstress.

FIRST MODIFIED EXAMPLE

FIG. 7 shows a plan view of the structure of a semiconductor chip SCused in a semiconductor device SD in a first modified example, andcorresponds to FIG. 2 according to the embodiment. FIG. 8 is an enlargedview of a main part of FIG. 7. The semiconductor device SD of thismodified example has the same structure as that of the semiconductordevice SD of the above embodiment except that the electrode pads PD ofthe semiconductor chip SC are arranged in a plurality of lines (forexample, in two lines) along each side.

In detail, the electrode pads PD are arranged along each side in astaggered manner. In any line, the relative position between the firstelectrode pad PD1 closest to the end of each side (that is, the cornerof the substrate SUB) and the first opening OP1 thereover in thismodified example is the same as the relative position between the firstelectrode pad PD1 and the first opening OP1 in the above embodiment. Ineach line, the relative position between the second electrode pad PD2and the second opening OP2 in this modified example is the same as thatin the above embodiment.

This modified example can also obtain the same effects as those of thisembodiment. In this modified example, in any line of the pads other thanthat on the outermost side, the relative position between the firstelectrode pad PD1 and the first opening OP1 thereover may be the same asthat between the second electrode pad PD2 and the second opening OP2.

This modified example can also obtain the same effects as those of thisembodiment.

SECOND MODIFIED EXAMPLE

FIG. 9 shows a cross-sectional view of the structure of a semiconductordevice SD according to a second modified example. The semiconductordevice SD of this modified example has the same structure as that of thesemiconductor device SD of the above embodiment or first modifiedexample except that the semiconductor device SD has a quad flat no-leadpackage (QFN).

In detail, a surface of the substrate mounting portion DP where thesemiconductor chip SC is not mounted is exposed from the seal resin MDR.A plurality of terminals TER are embedded in a surface of the seal resinMDR with the substrate mounting portion DP exposed therefrom. Theterminals TER are arranged along four sides of the seal resin MDR.

This modified example can also obtain the same effects as those of thisembodiment.

THIRD MODIFIED EXAMPLE

FIG. 10 shows a cross-sectional view of the structure of a semiconductordevice SD according to a third modified example. The semiconductordevice SD of this modified example has the same structure as that of thesemiconductor device SD of the above embodiment or first modifiedexample except that the semiconductor chip SC is mounted over the wiringsubstrate IP, such as an interposer.

Specifically, the semiconductor chip SC is held over the wiringsubstrate IP with an electrode formation surface of the chip facedupward. A terminal (for example, finger) over the wiring substrate IP iscoupled to the electrode pad PD of the semiconductor chip SC via thebonding wires WIR.

The semiconductor chip SC, the surface of the wiring substrate IP withthe semiconductor chip SC mounted thereon, and the bonding wire WIR aresealed by the seal resin MDR. In the example shown in the figure, theside surface of the seal resin MDR is flush with the side surface of thewiring substrate IP. Alternatively, the side surface of the seal resinMDR may be positioned inside the wiring substrate IP.

Solder balls SB are provided at the surface of the wiring substrate IPnot sealed with the seal resin MDR. Each solder ball SB is coupled tothe semiconductor chip SC via the wiring in the wiring substrate IP andthe bonding wire WIR.

This modified example can also obtain the same effects as those of thisembodiment.

Although the present invention made by the inventors has beenspecifically described based on the embodiment and modified examples,the present invention is not limited to the embodiment and modifiedexamples described above, and various modifications and changes can bemade to the above embodiment and modified examples without departingfrom the scope of the invention.

What is claimed is:
 1. A semiconductor device, comprising: a substrate having a first surface and a second surface opposite the first surface; a semiconductor chip having a first main surface, a second main surface opposite the first main surface and a first side on the first main surface, the semiconductor chip mounted on the substrate such that the second main surface being faced to the first surface of the substrate, a plurality of electrode pads arranged along the sides, an insulating film formed over the main surface and having a plurality of opening positioned over the respective electrode pads; a plurality of electrodes arranged along the first side of the semiconductor chip, each of the electrodes being connected with the electrode pads on the semiconductor chip via a plurality of wirings respectively; and a sealed resin body sealing the substrate, the semiconductor chip, the electrodes and the wirings, wherein the opening is smaller than the electrode pad, and wherein when the electrode pad closest to one end of the first side is defined as a first electrode pad, and the opening positioned over the first electrode pad is defined as a first opening, a center of the first electrode pad is positioned closer to the one end in a direction along the first side as compared to a center of the first opening.
 2. The semiconductor device according to claim 1, wherein when the electrode pad closest to a center of the first side is defined as a second electrode pad, and the opening positioned over the second electrode pad is defined as a second opening, a distance between a center of the second electrode pad and a center of the second opening is smaller than that between the center of the first electrode pad and the center of the first opening in the direction along the first side.
 3. The semiconductor device according to claim 2, wherein in the direction along the first side, a width of the first opening is the same as that of the second opening, and a width of the first electrode pad is larger than that of the second electrode pad.
 4. The semiconductor device according to claim 1, wherein the first electrode pad has a thickness of 1.2 μm or more.
 5. The semiconductor device according to claim 1, wherein the thickness of the insulating film is larger than that of the electrode pad.
 6. A semiconductor device, comprising: a rectangular substrate; a multilayer interconnection layer formed over the substrate; a plurality of electrode pads formed in an uppermost wiring layer of the multilayer interconnection layer, the electrode pads being arranged along a first side of the substrate; and an insulating film formed over the uppermost wiring layer, and having a plurality of openings positioned over the respective electrode pads, wherein the thickness of the insulating film is larger than that of the electrode pad.
 7. The semiconductor device according to claim 6, wherein the insulating film is a laminate including a silicon oxide film and a silicon nitride film which are stacked in that order, and wherein the thickness of the silicon oxide film is larger than that of the electrode pad. 